1. Field of the Invention
The invention concerns a process for the storage of heterogenous rubbish in holding or supply dumps such as rubbish bunkers or suitable rubbish containers before its removal and subsequent thermal utilization or a different processing operation.
2. Description of Related Art
Plants where wastes (such as domestic and special garbage, clearing sludge and industrial scrap) are thermally treated, have rubbish bunkers on the entry side. Relatively large quantities of these heterogeneous waste materials are stored temporarily or as a supply in the rubbish bunkers. These wastes, designated here as a whole using the term "rubbish", are a significant environmental risk due to their very heterogeneous composition and their usual storage quantities in the thousands of tons.
Ignition sources, such as furnace ashes, chemicals and metal parts are brought into the rubbish bunkers uninspected. Aerobic and anaerobic processes also take place in the rubbish bunker, despite the continuous exchange of air, which among other things can cause an increase in temperature to the point of spontaneous combustion. The ignition sources and the aerobic and anaerobic processes which can possibly cause combustion are collectively referred to as "disturbance law."
Rubbish bunkers are therefore a potential danger in the sense of the disturbance law. Disturbances result in considerable and extremely negative effects. Obviously these negative disturbances in the rubbish bunker can lead to other types of disturbances in other areas of the plant with even greater negative effects (J. Look, TUV Bayer/Sachsen, Safety Technology in Rubbish-incineration Plants with a View to the Disturbance Law. Conference on the Thermal Disposal of Wastes and Rubbish, Dec. 9-10, 1993, Cologne).
The significant hazardous materials released by burning are: heavy-metal compounds; acid gases; organic pollutants from the low-temperature carbonization of plastics; and polyhalogenated dibenzodioxins and furans as well as other carcinogenic materials.
The studies from the TUV Bayer/Sachsen(Look), cited above, document the potential qualitative and quantitative hazardous-materials in a manageable form.
The aerobic and anaerobic processes that take place in the rubbish bunker typically cause the temperature near the center of the rubbish pile to rise. Eventually the temperature can rise to the point of spontaneous combustion leading to smoldering fires which spread long unnoticed beneath the surface of the rubbish and are frequently difficult to reach. These smoldering fires in the bunkers of large plants can therefore persist for a long time, possibly several weeks.
The frequency and duration of the rubbish-bunker fires represent not only a considerable ecological risk, but also reduce the availability of the rubbish-incineration plants for other processing purposes and impair the safety of disposal.
Aside from the ecological and technical problems which a rubbish bunker fire brings with it, the economic burden is significant. Besides the interruption of operations and the halt to disposal thus associated with it, the partially burned rubbish, soaked with the fire-extinguishing agent, must be removed from the bunker after the fire has been put out along with all pollutants and disposed of elsewhere. The economic, ecological and technical damages borne by the operator of such plants are inadequately covered by insurance. Insurers find it difficult to estimate the risk of bunker fires, thus the already considerable insurance premiums continue to rise. Another factor which contributes to high insurance premiums is the possibility of litigation resulting from damage caused by the fires.
A further risk arising from the storage of rubbish in holding or supply dumps is represented by the methane buildup resulting from possible decomposition processes. When methane is mixed with air, an ignitable gas mixture is created which can lead to increased danger of explosion.
Measured against the possible expansion of a bunker fire and the dangers involved with the formation of ignitable gas mixtures, a possible attack upon the stored material by pests in the storage area is of course not as dangerous. However, here too, some precautionary measures must be taken.
It was and is therefore the concern of the technical world to recognize bunker fires early, to begin application of appropriate extinguishing means at the earliest possible time and to avoid the formation ignitable gas mixtures by intensive air circulation in the rubbish bunkers. The relevant state of the art has thus far been limited to fighting fires in the rubbish bunker only in the event of a blaze. Special precautionary measures for fire prevention are not available at this point.
Rubbish bunkers in conformity with the existing fire-protection requirements must, among other things, be equipped with fire walls, heat-resistant extraction devices, shutters on vents for smoke and heat, safety units supplied by emergency electric power, fire-monitoring systems and infrared cameras for possible localization of the site of the fire. Because rubbish-bunker fires are as a rule not on the surface, but develop inside the stored rubbish, the necessary technical means for fire fighting are inadequately suitable, despite infrared cameras, for pinpointing the locality of the fire precisely and fighting it efficiently, and are by no means suitable for preventing it before it arises.